Authorized September 30, 1933, under the National Recovery Act, construction was begun immediately on Bonneville Dam by the Army Engineer Corps. It was opened by President Franklin D. Roosevelt on September 28, 1937. Smaller than the Grand Coulee Dam farther up the river, the project provides flood control for the lower Columbia River, creates electric power for northern Oregon and southern Washington, and, by its locks, aids water transportation through the Cascade rapids to the upper Columbia.
Of the concrete gravity type, the dam has 18 vertical-lift, steel gates, 30 feet square, giving a spillway crest of 900 feet. The spillway is on the north side of Bradford Island, which divides the river into two channels at this point. On the south side are the powerhouse and navigation locks, connected to the spillway by a levee across the island itself.
The dam backs the river upstream, creating a lake extending 40 miles to The Dalles, with a minimum depth of more than 30 feet. The navigation locks consist of a single chamber, 76 feet wide and 500 feet long, with a minimum depth of 27 feet at low water. The water above the dam, being 72 feet above the river level, necessitates a lift of 59 feet—the highest in the world as of 1941.
Fish ladders and elevators allow salmon to ascend the river through the dam. One hundred fish pools, 40 feet long, 15 feet wide, and 6 feet deep, and each a little higher than the other, spiral to the top of the dam. Water cascades down this 5,900-foot watery stairway. The fish elevators work on a principle similar to canal locks; as chambers are filled with water and salmon they are lifted automatically to upper-dam level and dumped. To prevent fingerlings from being crushed in the giant turbine and generators as they make their way to the sea, the engineers have left openings large enough for the baby fish to pass through.
Right from the entrance to the Bonneville second powerhouse is the Fort Cascades National Historic Site. Park and walk up to the visitor center, the start of the mile-long walking trail of the camp and early settlement. Trail maps with information pertaining to each archeological location are provided.
